8.1L Vortec Specs: Horsepower, Torque & Everything on the Vortec 8100
The 8.1L Vortec (GM’s Vortec 8100, RPO L18) is a 496-cubic-inch big-block V8 that made 320–340 horsepower and 440–455 lb-ft of torque depending on the year. Look up the L18 RPO code in the FullSizeChevy GM RPO Codes Database for the factory option definition. It is a gasoline engine — not a diesel — and it was GM’s last big-block, built from 2001 to 2006 for heavy-duty trucks and SUVs.
8.1L Vortec (Vortec 8100 / L18) — Spec Sheet
| Spec | Value |
|---|---|
| Engine family | GM big-block V8 (Gen VII) |
| RPO code | L18 |
| Marketing name | Vortec 8100 |
| Displacement | 8.1 L / 496 cubic inches (8,128 cc) |
| Configuration | 90° V8, overhead valve (OHV), 2 valves per cylinder |
| Block / heads | Cast iron |
| Bore × stroke | 4.25 in × 4.37 in |
| Compression ratio | ~9.1:1 |
| Fuel system | Sequential multi-port fuel injection (gasoline) |
| Camshaft | Hydraulic roller |
| Horsepower | 320–340 hp @ 4,200 rpm (year/application dependent) |
| Torque | 440–455 lb-ft @ 3,200 rpm |
| Fuel type | Regular unleaded gasoline |
| Production years | 2001–2006 |
Horsepower & torque by application
GM rated the 8.1L differently across its run. In early Silverado/Sierra HD trucks it was rated at 340 hp @ 4,200 rpm and 455 lb-ft @ 3,200 rpm; later HD applications were listed closer to 330 hp and 450 lb-ft. What made the 8100 special wasn’t peak power — it was low-end torque: it’s making strong torque by ~1,200–1,400 rpm and holds it flat through the mid-range, which is exactly what you want for towing and hauling.
Displacement & design
At 496 cubic inches, the 8100 is a true big-block — the modern successor to the classic Mark IV/V big-block line, with a cast-iron block and heads, a 4.25-inch bore and 4.37-inch stroke, and a conventional pushrod OHV valvetrain. It uses sequential fuel injection and a hydraulic roller cam, so it’s more refined and more emissions-friendly than the older carbureted 454s while keeping the big-block torque character.
Which trucks and SUVs got the 8.1L?
The Vortec 8100 was a heavy-duty engine — you won’t find it in a half-ton. It appeared in:
- Chevrolet Silverado / GMC Sierra 2500HD and 3500 (2001–2006)
- Chevrolet Suburban 2500 and GMC Yukon XL 2500
- Chevrolet Avalanche 2500
- Medium-duty (Kodiak/TopKick), motorhome, and marine applications
Is the 8.1 Vortec gas or diesel?
It’s gasoline. The confusion is understandable — it’s a huge, torquey engine that competed with the Duramax diesel in the same trucks — but the 8100 runs on regular unleaded. If you want a diesel in that era’s HD truck, that’s the 6.6L Duramax; the 8.1L is the gas big-block alternative.
Is the 8.1L worth buying?
For its intended job — towing and hauling with simple, durable, non-diesel mechanicals — the 8100 has a strong reputation. It drinks fuel (it’s a 496 big-block), but it avoids diesel-specific repair costs and makes effortless torque. If you’re weighing it against the 6.0L, see our 6.0 vs 8.1 Vortec comparison, and if you’re shopping engines across the platform, the GMT800 engine guide breaks down every option.
Frequently asked questions
How much horsepower does an 8.1 Vortec have? Between 320 and 340 hp depending on model year, with 340 hp @ 4,200 rpm on early HD trucks.
How many cubic inches is the 8.1 Vortec? 496 cubic inches (8.1 liters).
Is the 8.1 Vortec a big block? Yes — it’s GM’s last production big-block V8.
Is the 8.1 gas or diesel? Gasoline.
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